Advance
Innovative Fortifications
Our genius in fortification does not represent a radical departure in their design; rather, the innovation comes from the placement of the fortresses. By taking maximum advantage of local terrain, even the most basic fort requires more effort and supplies to take.
FranceCountrypotentialAdvance tree
The game files don’t say where this goes: it has no requires, so the game places it in the 
Absolutism tree itself.
Modifiers
Fort Limit+20%
Definitionin_game/common/advances/country_FRA.txt:91
93content_priority = 1000